Apparatus and method for forming rectangular bottom plastic bag machine

ABSTRACT

The machine receives a continuous web of side-gussetted, flattened tabular bag material which has already been formed with a transverse bottom seal and transverse weakening perforations to be subsequently severed to form the open top. A pair of interrupted rotary motion, oppositely turning, resilient-surfaced rolls are grooved to receive vacuum tubes. As the web is pulled by the rolls, the vacuum splays the gussets outward to form triangular pockets of gusset material, providing openings for axially-moving fingers on the turning roll shafts to grip the outer corners of the bag bottom and pull the corners to about the bottom of the turning rolls, which then stop. Where the bottom is to be sealed, seal pads on opposite sides then move inward into the triangular pockets, there being a straight-longitudinal bottom edge as the base of the triangle. The fingers retract as the pads move inward. The bottom of the bag is now flat and open. Thereupon, a pair of heated seal bars engage the longitudinal bottom edges of the bag to form the longitudinal edge seals, the gusset material being held in position in the pads. The seal bars retract and the seal pads retract. After the bottom has been formed and optionally sealed, the rolls resume rotation and move the finished bag to the next station and feed the next bag to the fold station. A conveyor belt, travelling transversely, moves the completed bag to a position to be engaged by a set of rapidly rotating snap rolls which pull the completed bag apart from the web along the perforations.

United States Patent [191 Schaffron Nov. 13, 1973 [76] Inventor: Helmut T. Schaffron, c/o 710 Villanova Dr., Davis, Calif. 95616 22 Filedt Oct. 12, 1971 211 Appl. No.: 188,112

[52] US. Cl. 156/221, 156/223, 156/306,

156/465, 156/469, 156/538, 93/23 [51] Int. Cl B31b l/64, B3lf1/08 [58] Field of Search 156/221, 200, 287,

Bushbaum 93/23 Primary Examiner-Alfred L. Leavitt Assistant ExaminerBasil J. Le'wris Att0meyJulian Caplan [57] ABSTRACT v The machine receives a continuous web of sidegussetted, flattened tabular bag material which has already been formed with a transverse bottom seal and transverse weakening perforations to be subsequently severed to form the open top. A pair of interrupted rotary motion, oppositely turning, resilient-surfaced rolls are grooved to receive vacuum tubes. As the web is pulled by the rolls, the vacuum splays the gussets outward to form triangular pockets of gusset material, providing openings for axially-moving fingers on the turning roll shafts to grip the outer corners of the bag bottom and pull'the corners to about the bottom of g the turning" rolls, which then stop. Where the bottom is to be sealed, seal pads on opposite sides then move inward into the triangular pockets, there being a straight-longitudinal bottom edge as the base of the triangle. The fingers retract as the pads move inward. The bottom of the bag is now flat and open. Thereupon, a pair of heated seal bars engage the longitudinal bottom edges of the bag to form the longitudinal edge seals, the gusset material being held in position in the pads. .The seal bars retract and the seal pads retract. After-"the bottom has been formed and optionally seale dgthe rolls resume rotation and move the finished" bag to the next station and feed the next bag to the; fold'station. A conveyor belt, travelling transversely, moves the completed bag to a position to be engaged by a set of rapidly rotating snap rolls which pull the completed bag apart from the web along the perforations.

Patented Nov .13, 1973 I 3,772,116

5 Sheets-Sheet l INVENTOR.

A1 arney Patented Nov .13, 1973 3,772,116

3 Sheets-Sheet 2 I NVENTOR.

- Fig. 4

14 for/76g Patented Nov .13, 1973 3 Sheets-Sheet S llll Fig. 6

APPARATUS AND METIIOI; FOR FORMING RECTANGULAR BOTTOM PLASTIC BAG MACHINE This invention relates to a new and improved apparatus and method for forming rectangular-bottom plastic bags.

More particularly, the present invention relates to a machine and a method for continuously manufacturing plastic bags having rectangular bottoms which may be sealed by heat sealing means only, thereby eliminating the use of adhesive.

A further feature of the invention is the fact that mechanical means are only employed in the operation of the machine and it is adapted to a continuous, in-line operation. Optionally the machine may be out-of-line operation in that individual bag blanks may be fed.

A feature of the invention is the bag which is produced thereby. The bag is folded flat for transportation and storage; and when opened at the point of filling, the bottom is rectangular and assumes an open position transverse to the direction of the bag similar to conventional paper grocery bags. Bags made in accordance with this invention have the advantage that they stand upright and stable on counters or similar supports while being loaded, and hence leave both hands of the bag filler free for the loading operation; and further, the bags may be opened from flattened condition in a single manual snapping action similar to that used in opening conventional paper grocery bags.

It is, accordingly, a feature of the invention that the bags can be handled very similarly to conventional paper bags and no substantial changes in bag handling and loading techniques are required.

A principal feature of the invention is the fact that the machine is automatic in operation and requires little or no attention from themachine operator.

A further feature of the invention is the fact that the machine may be changed for different bag sizes with a minimum of effort and change parts required.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

FIG. 1 is a schematic perspective view showing a roll of bag forming material as received into the machine at the commencement of its operation.

FIG. 2 is a view similar to FIG. 1 showing the beginning of the opening of the gusset adjacent the eventual bottom of the bag.

FIG. 3 is a view similar to FIG. 2 showing the gusset full open at the bottom and showing the longitudinal bottom seal formed by the present invention;

FIG. 4 is a perspective view showing the completed bag full opened in condition for loading.

FIG. 5 is a side elevation of a machine in accordance with the present invention.

FIG. 6 is a side elevation of a portion of FIG. 5.

FIG. 7 is a fragmentary end elevation of the structure of FIG. 6.

FIG. 8 is a view similar to FIG. 6 showing the parts in a different position in the cycle of operation.

FIG. 9 is a side elevational view of the structure of FIG. 8.

FIG. 10 is a top plan of a pad used in the machine.

The material used to form bags in accordance with the present invention is a continuous web 11 of a plastic material which is initially tubular, and preferably seamless in initial shape, and which is, prior to being received in the machine, gusseted and flattened by forming gussets 12 in each longitudinal side edge. Where a longitudinal bottom seal is to be formed, the plastic material is heat-scalable. The inside edge 13 of the gusset is on the inside of the web. In the form shown in the drawings, the gusset is approximately one-third the total width of the web. There are two outside gusset edges 14 which extend longitudinally of the web.

At intervals there are formed transverse heat seals 16 which extend entirely across the width of web 11. The distance between seals 16 equals the height of the completed bag plus one-half the longitudinal length of the bottom. Immediately adjacent each transverse seal 16 is a series of perforations 17 which also extends across the web 11 and ultimately the bag is separated from the adjacent bag along perforations 17.

As shown in FIG. 3, the bottom which is formed in the bag by the present invention has transverse bottom edges 18 and longitudinal bottom edges 19, the edges 18, 19 forming the rectangular bottom. Immediately inward of edges 19 are longitudinal bottom seals 21, there being four such seals, two on each side and two on each longitudinal edge and two on each side of transverse seal 16. There is a double-walled triangular pocket 22 formed of gusset material to which the bottom of the bag is adhered by seal 21. Pocket 22 is fabricated in accordance with the present invention, and the seal is formed thereby.

Directing attention to FIG. 5, the machine of the present invention has a pair of main frame members 26 on either side. Side plates 27 are installed in the openings 28 at the top edges of plates 26. To the left, as viewed in FIG. 5, is a dancer bar assembly 31 which is conventional in plastic bag forming equipment and has a plurality of top and bottom rollers 32 around which the web 11 is reeved. Since the operation of the machine of the present invention is intermittent, while the manufacture of the web which is received in the machine is usually continuous, the dancer bar assembly 31 takes up the pulsations in movement of the web. From the dancer bar assembly, the web is fed over the top of idler roller 36. Positioned above roller 36 is a sensor 37 which senses the seals 16 or spots on the web 31 by various means, such as photocells, magnetic heads or pressure fingers. The position of sensor 37 is adjustable on its supporting arm 38.

From roller 36 the web 11 is fed over the top of top idler roller 41 which is mounted on plates 26 by pillow blocks 42 and thence vertically down into the machine.

A pair of tangent, horizontal-axis feed rolls 46, horizontally spaced apart, are mounted by means of horizontal transverse shafts 47 in plates 27. The circumference of each roll 46 is selected to feed web 11 the required distance to form the bag. Each roll 46 has a groove 48 spaced inward from each end edge. Fitting within each groove 48 is a vacuum nozzle 49 at the lower end of a vacuum pipe 57 which extends upward and out of the machine. The web 11 is pinched between the exterior of rolls 46 which turn in the direction of 5 the arrows in FIG. 5. The vacuum nozzles 49 pull the half the eventual width of the completed bag from transverse seal 16.

Driving belt 52 causes the feed rolls 46 to turn in unison under control of sensor 37. The movement of the rolls 46 is not continuous but is interrupted. Thus, the rolls turn from their initial position shown in FIG. 1 or FIG. 6 through about 75 to the position of FIG. 8 and then remain stationary during the sealing operation. Thereupon, the rolls complete the remaining 285 to their cycle.

Associated with each end of each roll 46 is a clamp arm 56 which reciprocates along, but is keyed to turn with, shaft 47. The inward movement of arm 56 is cushioned by a resilient pad 57 on the side of roll 46. The outer end of arm 56 is formed in a clevis 58 between the ends of which is a finger rocker 59 pivoted to the clevis by means of pivot 61 and carrying on its outer end (i.e., facing the roll 46) a finger 62. Spring 63 biases the rocker 59 in a clockwise direction as viewed in FIG. 7 so that the finger 62 is slanted downwardly inwardly. However, as the arm 56 is moved toward the roll 46 by means hereinafter explained, an adjustable screw 64 on arm 59 contacts the side of roll 46 and causes the arm 59 to pivot in a counter-clockwise direction as the roll 46 moves from the position of FIG. 6 to the position of FIG. 8. The entry of finger 62 into the gusset opening 23 as shown in FIG. 2, pulls the bottorn apart, as best shown in FIG. 3. The finger 62 is now being forced against the roll 46 and pinches the partially open bag on each side of the gusset against said roll. The end of the travel of finger 62 and roll 46 is controlled by a limit switch (not shown) which stops the rolls, and thereupon, clamp arms 56 are retracted by a time delay relay, or limit switch (not shown).

The inward and outward movement of clamp arm 56 sliding on shafts 47 is controlled by finger actuating cyl inder 66 which has rod 67. An offset connector 68 connects the inner end of the rod 67 to a pair of shifters 69 which slide in grooves '71 in arms 56. One cylinder 66 is located on each side of the machine and moves the pair of arms 56 on each side.

Where a longitudinal bottom heat seal is desired, seal pad slide rods 76 are positioned extending horizontally transversely between plates 27. Seal pad carriers 77 reciprocate on rods 76, one on each side of the machine. Carrier 77 is actuated by seal pad cylinder 78. On the top of each carrier 77 is a seal pad 81, the top surface 82 of which is pentagonal in plan (FIG. but its edges are formed in curved surfaces 83 which match the radius of the exterior of roll 46. The inner end of pads 81 are triangular and generally complementary to the shape of pocket 22. Retraction of the fingers 62 has left the bottom of the bag to be sealed in a relaxed position. By means of a limit switch (not shown), seal bars 86 are caused to move upwardly, each bar being controlled by rod 87 on vertically mounted cylinder 88 on carrier 77. The tip 89 of bar 86 is shaped to form the longitudinal bottom seal 21 and performs this operation as best shown in FIGS. 8 and 9. A time delay relay controls the return of the seal bar 86 to initial position, and when the bar 86 has thus returned, pad 81 is caused to retract and the rolls 46 resume their turning motion, feeding the finished bag downwardly and bringing the next bag into place.

Below the rolls 46 is a series of horizontal transversely moving conveyor belts 91 mounted on end roller 92 and drive roller 93, the roller 93 being grooved by means of grooves 94 to receive the belts 91. Above the roller 93 is a squeeze roller 96 which squeezes the bag against the roller 93 and causes the bag to be folded in the transverse folds shown in FIG. 4. Preferably, the peripheral speed of rollers 93, 96 is faster than the peripheral speed of rolls 46 and this causes the folded bag to be moved to the right as viewed in FIG. 8 at a greater speed than the movement of web 51. Hence the bag passing through rollers 93, 96 is pulled away from the next bag being formed along the perforations l7 which have been provided therefor. A stacker (conventional and not shown) stacks the bags into piles for packaging and transportation.

What is claimed is:

1. Apparatus for forming a flat, rectangular-bottom plastic bag wherein the bag stock is received by the apparatus in the form of a tube folded flat with a longitudinal gusset adjacent each longitudinal side edge, each gusset having an inside fold and a pair of outside folds and wherein a transverse heat seal is formed across the folded tube in the center of the bottom to be formed and wherein a longitudinal edge seal is formed on each side of the bottom of the bag, said apparatus comprising feed means for feeding the bottom end of the tube with an interrupted motion, and, on each side of the apparatus, spreading means including vacuum means for pulling said bag adjacent said outside folds on each side to spread the gusset partially apart, gripping means including pins movable to operative position within said partially spread apart gusset for fully spreading the gusset apart adjacent the transverse seal to a flattened condition, support means movable to operative position for supporting the bag material in fully spread condition with a pocket of bag material superdmposed behind a rectangular bottom, and heat seal means movable to engage the bag material on the side opposite said support means to force said bag material against said support means and simultaneously form a longitudinal heat seal of said bag material of said bottom to said pocket along a line perpendicular to said transverse seal and extending to either side thereof along the longitudinal edge of said bottom.

2. Apparatus according to claim 1 which further comprises a conveyor movable in a direction transverse to the direction of feeding of said feed means and positioned to receive said bag and squeeze rolls at the discharge end of said conveyor, the peripheral speed of said squeeze rolls being substantially greater than the speed of feeding of said bag stock by said feed means.

3. Apparatus according to claim 1 in which said feed means comprises a pair of resilient-surfaced tangent feed rolls, drive means for turning said feed rolls in opposite directions, said feed rolls formed with grooves adjacent each end, said spreading means comprising nozzles located in said grooves, and vacuum pipes for drawing vacuum in said nozzles, said nozzles positioned to pull bag stock overlying each said gusset in a direction perpendicular to said direction in which said bag stock is fed.

4. Apparatus according to claim 3 in which said gripping means comprises a clamp arm rotatable with each said drive roll on each end of each said drive means, means for reciprocating said clamp arms toward and away from said feed rolls, each said clamp arm having a finger and mounting means pivotally mounting said finger on said clamp arm, whereby as said clamp arm approaches said feed roll it enters into the partially spread apart gusset and clamps said bag stock against said feed roll as said feed roll and clamp arm turn together until the bag stock is spread apart in a flat bottom located transverse to the direction of feeding of said feed means.

5. Apparatus according to claim 1 in which said sup-' port means comprises a triangular-shaped pad complementary to said pocket and support means for reciprocating said pad in a direction transverse to the direction of feeding of said feed means, said pad entering said gusset to support the pocket.

6. Apparatus according to claim 5 in which said heat seal means comprises a heated seal bar, and bar reciprocating means mounted on said pad support means for reciprocating said seal bar toward and away from said seal pad.

7. Apparatus according to claim 5 which further comprises preliminary feed means for advancing bag stock in a continuous web to a position between said feed rolls, and timing means for turning said feed rolls and moving said clamp arms toward said feed rolls and turning said feed rolls and clamp arms approximately 75, then holding said feed rolls stationary, then moving said pads toward said feed rolls, then retracting said clamp arms, then moving said bars toward said pads, then retracting said bars and pads to initial position, then turning said feed rolls and clamp arms to initial position.

8. A method of forming a rectangular flat bottom on a bag of thermo-plastic material comprising feeding bag stock in the form of a tube folded flat with a longitudinal gusset adjacent each longitudinal side edge with each gusset having an inside fold and a pair of outside folds and formed with a transverse heat seal across the tube at the center of the bottom to be formed, said method comprising feeding said tube with said transverse heat seal first between a pair of feed rolls, pulling said gusset apart at locations spaced from said transverse heat seal about half the length of the bottom to be formed by drawing the opposite sides of said tube away by vacuum, and gripping the bag stock against the feed rolls to pull said tube to form a flat surface sym metric about said transverse heat seal and a triangular pocket of gusset material overlying the bottom, and supporting the bag stock in said flat surface at a position close to the periphery of said feed rolls and forming longitudinal seals on said flat surface by moving heated seal bars against said bag stock to seal said bag stock in said longitudinal bottom seal.

9. The method of claim 8 in which said tube is formed in a continuous web and with a transverse perforation spaced from said transverse heat seal and which further comprises further feeding said tube between said feed rolls after said longitudinal bottom seal is completed and gripping the tube with said feed rolls above said perforation and then pulling the completed bottom away from said perforation to separate the completed bag from said tube.

10. The method of claim 8 in which said step of gripping said bag stock comprises pinching said tube against said feed rolls at locations on either side of said transverse heat seal spaced from said transverse heat seal one-half the length of the bottom tube formed and turning said pinched locations with said rolls until said bottom is flat;

11. The method of claim 8 in which said step of supporting said bag stock comprises moving inwardly on either side of the bag a triangular shaped pad to support said pocket of bag stock material immediately beyond said flat surface in the direction of said rolls.

12. The method of claim 11 in which said step of forming longitudinal seals comprises compressing said bottom surface against said pocket to seal said bottom surface to said pocket and seal together the outer-edge of bag stock comprising said pocket in a line transverse to said transverse heat seal. 

1. Apparatus for forming a flat, rectangular-bottom plastic bag wherein the bag stock is received by the apparatus in the form of a tube folded flat with a longitudinal gusset adjacent each longitudinal side edge, each gusset having an inside fold and a pair of outside folds and wherein a transverse heat seal is formed across the folded tube in the center of the bottom to be formed and wherein a longitudinal edge seal is formed on each side of the bottom of the bag, said apparatus comprising feed means for feeding the bottom end of the tube with an interrupted motion, and, on each side of the apparatus, spreading means including vacuum means for pulling said bag adjacent said outside folds on each side to spread the gusset partially apart, gripping means including pins movable to operative position within said partially spread apart gusset for fully spreading the gusset apart adjacent the transverse seal to a flattened condition, support means movable to operative position for supporting the bag material in fully spread condition with a pocket of bag material super-imposed behind a rectangular bottom, and heat seal means movable to engage the bag material on the side opposite said support means to force said bag material against said support means and simultaneously form a longitudinal heat seal of said bag material of said bottom to said pocket along a line perpendicular to said transverse seal and extending to either side thereof along the longitudinal edge of said bottom.
 2. Apparatus according to claim 1 which further comprises a conveyor movable in a direction transverse to the direction of feeding of said feed means and positioned to receive said bag and squeeze rolls at the discharge end of said conveyor, the peripheral speed of said squeeze rolls being substantially greater than the speed of feeding of said bag stock by said feed means.
 3. Apparatus according to claim 1 in which said feed means comprises a pair of resilient-surfaced tangent feed rolls, drive means for turning said feed rolls in opposite directions, said feed rolls formed with grooves adjacent each end, said spreading means comprising nozzles located in said grooves, and vacuum pipes for drawing vacuum in said nozzles, said nozzles positioned to pull bag stock overlying each said gusset in a direction perpendicular to said direction in which said bag stock is fed.
 4. Apparatus according to claim 3 in which said gripping means comprises a clamp arm rotatable with each said drive roll on each end of each said drive means, means for reciprocating said clamp arms toward and away from said feed rolls, each said clamp arm having a finger and mounting means pivotally mounting said finger on said clamp arm, whereby as said clamp arm approaches said feEd roll it enters into the partially spread apart gusset and clamps said bag stock against said feed roll as said feed roll and clamp arm turn together until the bag stock is spread apart in a flat bottom located transverse to the direction of feeding of said feed means.
 5. Apparatus according to claim 1 in which said support means comprises a triangular-shaped pad complementary to said pocket and support means for reciprocating said pad in a direction transverse to the direction of feeding of said feed means, said pad entering said gusset to support the pocket.
 6. Apparatus according to claim 5 in which said heat seal means comprises a heated seal bar, and bar reciprocating means mounted on said pad support means for reciprocating said seal bar toward and away from said seal pad.
 7. Apparatus according to claim 5 which further comprises preliminary feed means for advancing bag stock in a continuous web to a position between said feed rolls, and timing means for turning said feed rolls and moving said clamp arms toward said feed rolls and turning said feed rolls and clamp arms approximately 75*, then holding said feed rolls stationary, then moving said pads toward said feed rolls, then retracting said clamp arms, then moving said bars toward said pads, then retracting said bars and pads to initial position, then turning said feed rolls and clamp arms to initial position.
 8. A method of forming a rectangular flat bottom on a bag of thermo-plastic material comprising feeding bag stock in the form of a tube folded flat with a longitudinal gusset adjacent each longitudinal side edge with each gusset having an inside fold and a pair of outside folds and formed with a transverse heat seal across the tube at the center of the bottom to be formed, said method comprising feeding said tube with said transverse heat seal first between a pair of feed rolls, pulling said gusset apart at locations spaced from said transverse heat seal about half the length of the bottom to be formed by drawing the opposite sides of said tube away by vacuum, and gripping the bag stock against the feed rolls to pull said tube to form a flat surface symmetric about said transverse heat seal and a triangular pocket of gusset material overlying the bottom, and supporting the bag stock in said flat surface at a position close to the periphery of said feed rolls and forming longitudinal seals on said flat surface by moving heated seal bars against said bag stock to seal said bag stock in said longitudinal bottom seal.
 9. The method of claim 8 in which said tube is formed in a continuous web and with a transverse perforation spaced from said transverse heat seal and which further comprises further feeding said tube between said feed rolls after said longitudinal bottom seal is completed and gripping the tube with said feed rolls above said perforation and then pulling the completed bottom away from said perforation to separate the completed bag from said tube.
 10. The method of claim 8 in which said step of gripping said bag stock comprises pinching said tube against said feed rolls at locations on either side of said transverse heat seal spaced from said transverse heat seal one-half the length of the bottom tube formed and turning said pinched locations with said rolls until said bottom is flat.
 11. The method of claim 8 in which said step of supporting said bag stock comprises moving inwardly on either side of the bag a triangular shaped pad to support said pocket of bag stock material immediately beyond said flat surface in the direction of said rolls.
 12. The method of claim 11 in which said step of forming longitudinal seals comprises compressing said bottom surface against said pocket to seal said bottom surface to said pocket and seal together the outer-edge of bag stock comprising said pocket in a line transverse to said transverse heat seal. 